1. Field of the Invention
The present invention relates to a process for preparing hydrogen peroxide from the reaction of oxygen and/or oxygen-delivering substances with hydrogen and/or hydrogen-delivering substances in the presence of a catalyst.
2. Discussion of the Background
Most hydrogen peroxide produced commercially is obtained via the anthraquinone process involving the oxidation of an anthra-hydroquinone in the presence of air (yielding the hydrogen peroxide) and the recycling reaction of reducing the resulting anthraquinone to anthra-hydroquinone in the presence of a noble metal catalyst, most commonly Pd. A catalyst free of noble metals is described in WO 97/01113. The formation of hydrogen peroxide from the elements is not of significant commercial importance at this point. However, for specific applications, e.g. in electronics, ultrapure hydrogen peroxide is required. In this context, producing hydrogen peroxide from the elements may be cost-effective over working-up and cleaning hydrogen peroxide obtained by the anthraquinone process.
In a promising novel and alternative strategy to create micro- and/or mesoporous catalytically active materials in general, metal ions and molecular organic building blocks are used to form so-called metal-organic frameworks (MOFs). The metal-organic framework materials as such are described, for example, in. U.S. Pat. No. 5,648,508, EP-A-0 709 253, M. O'Keeffe et al., J. Sol. State Chem., 152 (2000) p. 3–20, H. Li et al., Nature 402 (1999) p. 276 seq., M. Eddaoudi et al., Topics in Catalysis 9 (1999) p. 105–111, B. Chen et al., Science 291 (2001) p. 1021–23.
Among the advantages of these novel materials, in particular for applications in catalysis, are the following:                (i) larger pore sizes can be realized than for the zeolites used presently;        (ii) the internal surface area is larger than for porous materials used presently;        (iii) pore size and/or channel structure can be tailored over a large range;        (iv) the organic framework components forming the internal surface can be functionalized easily;        (v) the metal-organic framework according to the invention is stable even if no host, solvent or any other additional substance is present, i.e. the framework does not collapse and/or interpenetrate and/or change its shape and dimension. This puts the material according to the invention in contrast to other metal-organic materials that maybe used as catalysts.        
However, these novel porous materials have only been described as such. The use of these catalytically active materials for the reaction of hydrogen and oxygen to form hydrogen peroxide has not been disclosed yet. In related applications, the use of these novel porous materials as shaped bodies (U.S. application Ser. No. 10/157,182) and for epoxidation reactions (U.S. application Ser. No. 10/157,494) has been described.